1. Field of the Invention
Exemplary embodiments of the present invention relate to a distributed feedback-directly modulated laser (DFB-DML).
2. Discussion of the Background
Recently, LTE backhaul is fast-growing market and the market is expected to support 100 million mobile devices by 2015. As the number of subscribers increases, efforts to decrease the cost per subscriber increase. A considerable portion of the cost is occupied by a laser source. Therefore, a low-cost distributed feedback-directly modulated laser (DFB-DML) is a good candidate for cost-effective optical networks. The DFB is a type of laser diode where an active region of the laser is periodically structured of diffraction grating. The grating provides optical feedback for the laser and reflects only a narrow band of wavelengths. Therefore, the DFB produces a single longitudinal lasing mode and has high Q-factor.
In comparison with externally modulated lasers (EMLs), the directly modulated lasers (DMLs) have many advantages of cost, power consumption and size. However, direct modulation induces frequency chirp. Over the data rate of 3 Gb/s, the frequency chirp combined with fiber dispersion degrades system performance. Therefore, several investigations have been conducted to compensate the penalty due to the frequency chirp. Some research have devised optical domain solutions such as specially designed chirp-managed lasers using optical spectrum reshaper (OSR) filter and dispersion compensation fiber (DCF).